Mystery of astronomy solved? – Too many galaxies discovered in old images

A British research group has discovered so unexpectedly many previously invisible galaxies in the deepest far-infrared image of the universe that confirmation of the find would "blow up current models of the number and evolution of galaxies". This was announced by the Royal Astronomical Society, which explained that the work was based on data collected by ESA's Herschel space telescope, which was shut down more than ten years ago. The previously hidden population of galaxies was found by overlaying 141 individual images. Research leader Chris Pearson said that research with Herschel had been pushed to its absolute limit.

Too many galaxies discovered

As the British research center RAL Space, which was also involved in the work, recalls, galaxies can be detected in the so-called far infrared spectrum that are otherwise obscured by dust. However, it is precisely this dust that can ensure that they form stars particularly intensively and are of great importance for understanding the universe. To detect them, the so-called "Herschel-SPIRE Dark Field" was created by superimposing the Herschel images. This image, by far the deepest in the far infrared spectrum, was then so full of galaxies that new methods had to be developed to distinguish and count them.

The indications discovered in this analysis of a previously undetectable population of particularly faint galaxies had not been predicted by current models of the cosmos, the team writes further. If their existence is confirmed, this could explain all the remaining infrared energy in the universe, the origin of which has so far been a mystery. At the same time, however, the existing models for the formation and evolution of galaxies would have to be revised, as the discovery has virtually blown them apart.

"The discovery shows how valuable the archive of Herschel data is," adds astrophysicist David Clements. Although it has not been working for more than ten years, "we are still getting great new results". For more data in the analyzed wavelengths, however, new and better instruments are needed. The research team is hoping for the proposed PRIMA space telescope for research in the far infrared spectrum ("Probe far-Infrared Mission for Astrophysics"). The US space agency NASA plans to decide on its realization next year. The research into the previously hidden galaxies is now being presented in the Monthly Notices of the Royal Astronomical Society .

(mho)